The present invention relates to increasing the electric breakdown voltage of gas-insulated high voltage devices. Particularly and, for example, the invention relates to improvements of the insulative properties of devices such as high voltage cable or high voltage generators with an SF.sub.6 atmosphere between the different conductors or electrodes.
The electric strength of high voltage devices with gas insulation is quite frequently reduced due to the presence of solid state impurities such as dirt, dust or other particles floating in the gaseous space of the insulation. Usually, the presence of certain amount of density of such particles must be expected and it is necessary to take such impurities into consideration upon dimensioning and proportioning the device. Particularly, a larger distance between the conductors of different voltage potential must be chosen or the gas pressure must be increased, or both steps must be taken. That, however, is quite undesirable so that usually the gas atmosphere is cleaned beforehand.
Filtering of the gas and cleaning all parts interfacing with the gas, permits indeed, a drastic reduction in the dust etc. concentration. There is, however, a practical limit here so that some foreign particles will remain and removal thereof is usually too expensive, so that it is more economical to offset their presence by higher distances or higher pressure. Clearly, there is a need for simplified purification of the gaseous insulative atmosphere in high voltage devices.